This invention relates to antipilferage tags and to systems using such tags.
Antipilferage tags or markers are applied to articles of commerce in order to protect them from theft at the point of sale premises. Typically, the tag is a magnetic medium which is deactivated when a shop assistant carries out the routine procedure at the time of effecting a sale. Such deactivation prevents detection of the magnetic tag when it (and the article to which it is attached) passes through a detection system, typically in the form of a walk-through framework which emits an alternating matnetic interrogation field. This field is designed to interact with a tag and to respond by, for example, emitting a warning signal in the event that detection of a non-deactivated tag occurs.
Instead of arranging for the interrogation gate to emit a warning signal in the presence of a tag, an alternative system is to use the tag itself to generate an alarm signal, e.g. a high frequency tone. This can theoretically be achieved if the tag contains the circuitry required to detect the interrogating field and to respond to that field. This approach requires the incorporation of fairly sophisticated technology into what would otherwise be a relatively small and inexpensive article, the end porduct being termed a "smart tag" or an "active tag".